The study was carried out on 23 entries of Origanumcollected from different areas
of south Italy. The 23 entries were characterizedvia determining the chemical composition of
their essential oils and genetic variability. The gas-chromatography of the essential oils of
oregano accessions allowed the detection of 44 components with the predominance of
carvacrol, thymol, linalyl acetate, γ-terpinene, o-cimene, s-caryophylleneand cis-ocimene. A
high variability in the main components concentration was revealed except in the case of the
accessions 13, 14 and 15 where the linalyl acetate ranging between 51.27 and 60.93%,
outlining a new oregano chemotype.Using hierarchical cluster analysis, four main groups of
samples were observed. Genetic variability using the RAPD analysis was not able to reveal
clear polymorphism PCR patterns useful to distinguish the entries.So that, we decided to
conduct further molecular analyses to determine the genetic variation among the entries under
investigation, using AFLPs a powerful tool to perform phylogenetic analysis. This technique
shows a high capability in detecting genetic variation. Combination between fluorescent
system and polyacrylamide gels allows obtaining large number of bands (225 to 557). Finally,

thecurrent study shows thatthe Dendrogram of genetic similarity of Origanum is widely
variable amongst genotypes of this plant.

Keywords:Origanumspp, Essential oil, Gas chromatography–mass spectrometry,Random
Amplification of Polymorphic DNA,Amplified fragment length polymorphism.